US 7019708 B2
A dual-band, dual-polarization LOS/SATCOM antenna having a plurality of omnidirectional elements surrounding a directional element. When the antenna is in an omnidirectional radiating mode, the directional element is disconnected from the circuit and only the omnidirectional elements radiate. The directional element has radiators at one end. When the antenna is in a directional mode, the omnidirectional elements fold out to be perpendicular to the transmission axis and serve as reflectors for the driving radiators, which also fold to be perpendicular to the transmission axis. The radiators and elements are adjustable in length to provide added gain.
1. An antenna assembly comprising:
an antenna/radio interface;
a body section connected to the antenna/radio interface; and
a plurality of omnidirectional radiating elements connected to the body section and surrounding a directional radiating element assembly, the group of omnidirectional radiating elements having a first position within the body section for an omnidirectional mode of the antenna assembly and a second position within the body section for a directional mode of the antenna assembly.
2. The antenna assembly according to
3. The antenna assembly according to
a switch for selecting between one of the omnidirectional mode and the directional mode of the antenna assembly; and
at least one matching circuit.
4. The body section according to
5. The antenna assembly according to
6. The antenna assembly according to
7. The antenna assembly according to
8. The antenna assembly according to
9. The antenna assembly according the
10. An antenna assembly comprising:
an antenna/radio interface;
a body section connected to the antenna/radio interface; and
a group of omnidirectional radiating elements connected to the body section and surrounding a directional radiating element assembly, the group of omnidirectional radiating elements having a first position within the body section for an omnidirectional mode of the antenna assembly and a second position within the body section for a directional mode of the antenna assembly, wherein the directional radiating element assembly includes an elongated section having a first end and a second end with the first end connected to the body section of the antenna assembly and the second end having two radiators.
11. The antenna assembly according to
12. The antenna assembly according to
13. The antenna assembly according to
14. The antenna assembly according to
15. A dual-band antenna comprising at least one omnidirectional radiating element and a directional radiating element located on a body section, with the directional radiating element having at least two radiators and the body section having a first position for deploying a plurality of reflectors and a second position for storing a plurality of reflectors, wherein the reflectors only function as reflectors when in the first position.
16. The dual-band antenna according to
17. The dual-band antenna according to
18. The dual-band antenna according to
19. The dual-band antenna according to
20. The dual-band antenna according to
21. The dual-band antenna according to
22. The dual-band antenna according to
23. The dual-band antenna according to
24. The dual-band antenna according to
25. The dual-band antenna according to
1. Field of the Invention
This invention relates in general to antennas and more particularly, to mult-band, multi-function antennas.
2. Description of the Related Art
In civilian life, wireless communication has become a luxury many feel they can't live without. In military operations, that may literally be true. In the field, soldiers must be able to communicate reliably and efficiently with others on the land, in the air, sea, and on the opposite side of the world. Wireless communication is accomplished through use of a radio, which is well known by those having ordinary skill in the art, connected to a radiating element, or antenna, also well know by those having ordinary skill in the art. An antenna is an impedance-matching device used to absorb or radiate electromagnetic waves. The function of the antenna is to “match” the impedance of the propagating medium, which is usually air or free space, to the source. Radio signals include voice communication channels, data link channels, and navigation signals.
Communication with those on the ground is most easily accomplished with radiating elements commonly called “monopoles” or “dipoles.” A dipole has two elements of equal size arranged in a shared axial alignment configuration with a small gap between the two elements. Each element of the dipole is fed with a charge 180 degrees out of phase from the other. In this manner, the elements will have opposite charges and common nulls. A monopole, in contrast, has only one element, but operates in conjunction with a ground plane, which mimics the missing second element. The physics of monopoles and dipoles are well known. Monopoles and dipoles, however, are efficient only for line-of-sight (LOS) communication. Obstructions such as mountains, or great distances, relative to the curve of the earth's surface, between the transmitter and receiver can prevent the reception of these signals. The relative positions of the transmitter and receiver, as well as the power output of the transmitter thus control whether the LOS signal will be received.
To overcome the effect of LOS obstacles, satellite communication (SATCOM) has been developed. Satellites are transceivers that orbit the Earth and can relay communications back and forth from the Earth's surface or to other satellites, allowing communication virtually anywhere in the world.
One of the characteristics of antenna transmission is “polarization,” which describes what physical plane the signal is being transmitted in. A dipole or monopole oriented in a vertical position (perpendicular to the earth's surface) radiates signals with a vertical polarization. For a second antenna to receive maximum signal strength, it too must have a vertical orientation. As the receiving antenna is rotated away from vertical, its maximum receive power diminishes until the antenna reaches a horizontal orientation (perpendicular to the transmit antenna), at which time the maximum receive power reaches zero.
Because satellites orbit the earth and transmit to receivers in multiple directions and orientations, single plane transmission is not efficient. Therefore, satellites transmit signals in a “circular” polarization. In this manner, the signal is transmitted in a continuous right-hand rotating orientation. A circularly polarized antenna has two dipoles arranged orthogonal to one another. The dipoles alternate “firing” with a positive charge rotating sequentially around the four individual elements and a negative charge on its axially oppositely aligned second element. When viewed on a three-dimensional time vs. polarization graph, the circularly polarized signal resembles a helix.
Due to the above-mentioned inherent loss in perpendicularly oriented linearly polarized transmitting and receiving antennas, a linearly polarized antenna will suffer from a 50% (3dB) signal loss when receiving satellite communication signals. Thus, a more efficient receiving means is desired.
“Man-Pack” radios are mobile radios designed to be carried or worn on a person. Currently Man-Pack radios are used by Military or Paramilitary soldiers in the field and used on the move or at halt. These radios employ a traditional monopole LOS antenna, which suffer from the above-mentioned inherent 3dB loss due to the polarization losses.
Portable SATCOM antennas, which are directional and circularly polarized, are available, however carrying two separate antennas is cumbersome. In addition, disconnection of the LOS antenna and connection of, and assembly or disassembly of a separate SATCOM antenna is usually burdensome to an excessive degree.
Accordingly, a need exists for a portable, lightweight, efficient, multiple band, multiple polarization, LOS/SATCOM antenna communication system in the form of a single unit that can easily be deployed in the field.
The present invention antenna system provides a lightweight and easily carried multiple band, multiple polarization antenna communication system. In a directional mode, the antenna system provides a fully capable, directional, antenna system of circular polarization especially suited for satellite communication but usable for other purposes. In an omnidirectional mode the antenna system provides a fully capable, omni-directional, antenna system of vertical polarization especially suited to line-of-sight communication, but usable for other purposes.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward.
Exemplary Embodiment of a LOS Antenna:
Described now is an exemplary antenna configuration for an omnidirectional vertically polarized communication mode of the inventive multi-band antenna according to an exemplary embodiment of the present invention. With reference to
Referring now to
Antenna 100 is shown in its omnidirectional configuration mode in
When the antenna 100 is in the omnidirectional mode, an electrical path is created from the radio/antenna interface 201, through the body 202, to the omnidirectional radiating elements 203. Radio/antenna interface 201 provides an electrical connection from the omnidirectional radiating elements 203 to a radio (not shown).
When the antenna is in the omnidirectional mode 302, the omnidirectional elements 203 are secured in a position substantially parallel to the directional element 204. However, the antenna 100 may be tuned by varying the omnidirectional elements 203 between parallel and horizontal to the directional element 204. The omnidirectional elements 203 are excited via an electrical path from the radio/antenna interface 201 through switch 301 to the omnidirectional elements 203. In this configuration, when a radio (not shown) is connected to the antenna 100 through the radio/antenna interface 201, a monopole antenna is realized. In this mode, the radio acts as the ground plane. In this manner, a vertically polarized, omnidirectional signal is transmitted and/or received.
For the most efficient radiation and reception of RF signals, as shown in
Referring again to
Exemplary Embodiment of a SATCOM Antenna
In a second configuration, the directional mode of the antenna 100, the antenna 100 will be physically converted to a directional antenna. To accomplish the conversion, omnidirectional elements 203 will be repositioned, as shown in
Referring now to
As can clearly be seen in the
The radiators 205 are shown in
The portion of the output wave launched by the radiators 205 that reaches reflectors 203 is reflected back in a direction toward the radiators 205 and added to the output wave already traveling in the direction away from the reflectors 205. As a result, the antenna 100 in its directional mode outputs little or no energy in the area behind the reflector, thereby creating a directional circularly polarized output signal.
Additional gain can be realized by providing additional radiators to the end of directional element 204. Additionally, the radiators 205 and omnidirectional elements 203 can be repositioned, or “folded” and “unfolded,” through the use of pivoting joints, springs, hinges, removal and insertion into another insertion port, or one of many other methods of repositioning and reorienting an element. It is desirable that an electrical connection be maintained to the elements 103 and 105 throughout a lifecycle of many folds and unfolds of the elements 103 and radiators 105. Finally, all elements and radiators can advantageously telescope to reduce the size of the assembly.
While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions and equivalents will occur to those skilled in the art without departing from the spirit and scope of the present invention as defined by the appended claims.